Reflector for headlamps



AC. N. WEEIVIS. `REFLxicToR FOR HEADLAMPS.

y APPLICATION FILED MAR-25,1920 1 v 1,3999?, Patented Dec. 6,192l A 3 SHEETS-SHEET 1. l h an I zllflllq' 23a INVENTOR c. N. wEEMs.

aEFLfcToR Fos HEADLAMPS.

yPPLICATIN FILD. MAR. 25, 1920.

. Patented Bec. 6, i214 3 SHEETS-SHEET 2.

`l Jg.; 5:

INVENTOR o. N. vI/EEMSvl` REFLECTOR fon HEADLAMPS, APPLICATION FILED MAB. 25, 1920.

Patented Dee. r6, 1921.

3 SHEETS-SHEE,T 3l

HORIZCNTAL Axl S HORIZONTAL A |5 ATT RNEY CHESTER N. WEET/IS, OF LIBRARY, PENNSYLVANI.

REFLECTOR FOR HEADLAMPS.

Specication of lLetters Patent.

Patented Dec: 6, 1921...

Original application filed June 19, 1919, Serial No. 305,292. Divided and this application filed March 25,

To all whom it 'may concern.'

Be 1t known that I, CHESTER V a citizen of theUnited States, and a resi- -dent of Library, county of Allegheny, and

State of Pennsylvania, have invented certain newl and useful Improvements in Re'- flectors`for Headlamps, of which the following is a specification. K

This invention is designedV to provide reflectors for a headlamp in which the source J of light,vusually an electric lampi, with said associated reflectors illuminates uniformly the curved inside surface of the lowerhalf A -of an `imaginary horizontal cylinder Whose axis vcoincides with the horizontal axis of the headlamp, whose radius is equal tothe height at which it is proposed to place the headlamp above the ground, and which extends' from a point slightly ahead of the headlamp toa distance offrom 200 feet to several hundred yards aheadof the head` la'mp, depending upon the type Of Vehicle upon which the headlamp is used. For use on pleasurevehicles this imaginary' cylinder would start approximately 2O feet and would extend about 200 feet ahead of the l the headlamp.

.. beam of light is secured, no portion of which v strikes'above the level of the center point` of the headlampg. v

The invention is further designed to provide a reflector `that is `constructed on a curve relative to the light source, which curve has been determined mathematically, so that a given surface before, the headlamp is illuminated substantially uniformlyof-its area,'which surface is the inside curved sur-A face of the lowerlhalf of the horizontal cylinder whose laxis coincides with the horizontal axis of the headlamp. y

The invention ,further vcomprises a reflector made according to La principle to'be hereinafter more fully described and also embodied i the claims, and in the preferred form of lamp I employ three re-f Serial No. 368,490.

fiectors, the functions of these reflectors, when assembled, being to intercept and refiect to the desired field all the light flux from the electric lamp,` except thatvlight flux which falls naturally and directly to the field from the electric lamp.

In practice, the beam of light flux will be spread slightly, due to the 'fact' that the source of light is of finite` size. The theoretical field to be illuminated is selected sufficiently near to the headlamp so that the spread of the light beam in practice will not be sufficient to elevate any light rays above the horizontal planeof the headlamp.,` and in designing any particular headlamp I select the position of the theoretical field to be Ailluminated in regard to the sizelof the filament ofy Athe particular electric lamp which is to be usec. The largerthevolume of the filament, the nearer it is necessary to 'assume the farther limit of the `theoretical field to be,illum inated,.because a large filament will spread the beam toa greater degree than a small filament. Y

A reflector made according to this invention is applicable to different forms ofVV lights, but particularly to that form as illustrated and described in my Patent No.

1,349,642, issued Aug. 17, 1920.

The invention is illustrated in the accompanying drawings, Ain which Figure l is a section on line 1-1 in Fig. 2. Fig. 2 is a front view, broken away to more clearly illustrate the construction. V Figi 3 is a section on line 3-3 in Fig. 2.` Fig. 4:.is a det-ail section of the lamp supporting fixture. Fig.

5 isa face view of part of the structure shown in Fig. 4.' Figs. 6, 7 and 8 are diagrammatic views showing the curvature of the reHectors and their correlation.

' The. 4lamp body' comprises' a casing 10,v

which is provided on the front with a lid or' door 11, which is fastened in any suit-- able way, such as by the hinge 12 and the catch 13, the rim of the door being provided with suitable means, such as the clip` 14, for holding a Acircular piece of clear or transparent glass 15.4 A snug fit is 'securedby means of a washer or gasket 16. A horizontal support or partition 17 is placeds within the casing and has its outline fitting the inside .of the casing l0 and' being se` .cured thereto by screws 18, although it will be evident that other means. of fastening these elements can be employed.

The horizontal support or partition 17 is provided with an opening 19, and in rear of the opening is mounted the lamp supporting fixture, which consists of a stationary member 20 secured by suitable means, such the screws 21, and a movable member 22 A lamp fit into slots 31 in the member 22,` so

that when the lamp is pushed in and then to the right, the lugs 30 are seated i'n the slots, the lateral portion of the slot extending a distance but little greater than the diameter of the guiding lugs almost at right angles to .the main portion of the slot.

The springs 32 are secured to the inner side of the sleeve 22 and are insulated there-l from by a suitable insulation 33, these springs having contactends 34 which lit against the contacts 35 at the end of the base 2 8 of the electric lamp bulb and act to complete the circuit with the lamp, and also by their spring pressure tend to hold the lamp in position, the `springs 32 having the wires 36 secured thereto b'y soldering or other suitable means, the wiresI 36 ex-` tending to the outside of the' casing, preferably A through theV supporting post 37,`

which is hollow and which is suitably secured to the casing of the headlamp and thereby acts asa support therefor.

The associated reflectors that` cooperate to direct the beam of light in the desired direction' consist 'of an upper'reflector '38, which is preferably secured to the supporting4 plate or partition 17 'by means of its flange 39, and -a` lower reflector 40 similarly secured by a similar ange, and forward reflectors 41 and 42, preferably formed 'of sheet metal and having" a'iiange 43 which rests on and is preferably riveted orlscreWed to the partition or support 17.

It will thusbe seen from this *descrip-` tion that the lamp casing and the elements on the inside .thereof are held together in a compact and stable manner, and the central support, while notessential, is preferable in providing a convenient means for supporting the reflectors 41 and 42 andx also for supporting the electric bulb preferably at an angle of about twenty-five degrees to the horizontal axis lof the lamp.

The reflectors 38 yand 40 are themain rhefiectors, mounted in the usual position in rear of the electric lamp or other source of illumination, and reflectors 41 and 42, which will be hereinafter referred to as the auxiliary reiiector and mentioned as one reflector, are mounted on the upper side of the supporting plate or partition 17 in front of the electric lamp. Each of these three reiectors is designed to distribute the light flux which it intercepts uniformly over the assumed'field hereinbefore mentioned, to wit: the inside curved surface of the lower half of an imaginary cylinder whose radius is the distance from the ground to the horizontal axis of the lamp, in practice this radius. being usually 42 inches, and the roadway` assuming level ground, will be approximately,uniformly illuminated over a strip approximately 40 feet wide and 200 feet long, starting 2O feet ahead of the automoloileA and extending straight ahead. The ground to the'sides -of this strip will also be illuminated, but to a lesser degree, and objects 'having elevation and situated ahead bf theautomobile vwill be illuminated by the direct beam to a height of 42 inches above the ground level.

It will be understood that any two or4` any three of these reflectors may be employed, and, if desired, the auxiliary re- Hector may be omitted and the tip of the electric lamp frosted, but I prefer, how ever, to use them in correlation as illus,u

trated herein. These reflectors are usually made of sheet metal polished on the inside surface. i

"lhe refiector 38 is generated by revolving aplane curve through substantially a 180 degree dihedral angle, the plane of the generating curve being at all times common to the horizontal axis of the headlamp.

In hthe following description the auxiliary reflector will be designated by the reference numeral 41 to indicate the two sections 4I 'and 42 thereof, Vin order to simplify the description.

The generating'curve ofthe reflector 38 is designed in the'following manner:

In Fig.V 6, AB `'s a given line .m distant and Parallel to a` horizontal line LM.k Point A, the starting point of line AB, is distant a from a' perpendicular dropped from point L on line. LM '-to C on line AB extended. Lines LB, LD1 and LD2 are common to vpoint L and intersect AB at about equal distances starting at B, and malte a variable angle phi (qi) with, line LM, the angle qs being considered as the angle for LB, LDlor LD2, though its value for each its is, of course, different. Point F is located l a O'iven .distance p from L along the line Lf, are 1in@ LF making an angie has (a) with the line LM. F is the starting point of a curve Fallahcl which is made u of sections of paraboles, F all, didn chris, ctc. The portion of this curve Fd, is small 4 renacer 'small parabolic section Fd1 is the line 1K1.. and that for the section dldz is I1K2etc.

According to thelaws of the parabola, 4the line ZF, which is a perpendicular from point F tothe directrix 1K1, is, equal -in length to the line LF. The point al, is common to two parabolic sections, and the perpendicu-l lars 1K1 dropped from this point to each directrix IK, and 11K, are the same length and equal to the line Ldl. For similar reasons the lines 52K2 are of the same length and equal to the line Ld2.

Now if curve Fcllalzul.3 werev a line on the surface of a reflector and a point source of light were placed lat L, the lightrays which strike the portion of the curve Fd, will all be reflected in the direction of and parallel to the axis LB. At point d, the direction of the curve `changes, and for. vthe distance '(Zld, the light rays will be reflected' in the direction of and parallel to the axis LDI.

- lt follows, of course, that the light' striking the curve @da will be reflected along the direction of and parallel'to the axis LDT I The values represented by the lines and angles of Fig. 6 are' of .any values whatso' ever, and ifhwe consider the reflector curve Fclldzda very small compared with the line AB and a great distanceaway from the latter, we will have, witha point source of light placed at L, spots of light along the line AB, the spot at B coming frointhe portion of curve 'F (l1, vthat at D1 coming from dirk, and `that at D2 coming from dads.

Tf now a. reflector surface is generated 'by revolving curve Follclzd through the 180 degrees dihedral angle above the horizontal plane through t-he line LM and around LM as an axis, andthen a pointsource of light [is-placed at L, the spots of light at B,

D1 and D2 referred toiabove will be replaced by semi-circular zones of light on the inside curved surface of thelower half ofthe horizontal cylinderI generated by. revolving the line AB aboutwthe line LMas an axis.

Now 'if instead of drawing the sections of the reflector curve Fall, dldz, dzda, etc., large as shown in Fi'gf, but on the other hand we draw them infinitely small and place an infinite number of su'ch parabolic` sections in the generating curve, the result in the final reflecting surface generated by revolving the curve about the line LM as explained above will be an infinite number of semi-circular zones of light on the inside curved surface of the lower half ofthe In each case it will' cylinder AB, yand the space between these zones will be infinitely `small,or, in other words, the light will be continuous over this illumina-ted surface. Such a `generating curve is illustrated by the dot-ted curve FJ in Fig.` 6 of the drawings.

If in designing the reflector Fd1d2d3, a circle EFE is first described through the point F with L as its center and the terminating points for the parabolic sections, that is, points F, all, d2, 'cI/i3, etc., are then so located that the distances between any -two adjacent perpendiculars to the line LM (or LM extended), dropped from the intersec# ti`on with this circle of each focal radius from point L to theseipoints, are equal, the amount of light on the illuminated zones on theinside .of the cylinder AB would be equal. These perpendiculars meet LM at F', rll, d'2, etc. This condition is true because the amount of light flux intercepted by each parabolic section Fall, lldz, olgdn, etc., is measured by the area of the spherical zone generated by the small arc on circle EFE subtendedl by the angle made by the lines from L to the ends of the small parabolic sections, assuming the circle EFE to be revolved aboutthe line LMl inthe same manner as the curve. The areas of these spherical zones are in turn `proportional to their altitudes, which are the lines Foll, d1d2, clgcl, etc., and these altitudes, as stated above, are taken equal in length.

With thelinal reflector in which an infinite number of sections or steps are taken in. making up the generating curve FJ there will be, therefore, on the inside curved surface of the horizontal cylinder AB an infinite number of small semi-circular vzones of light, each illuminated by the same amount of light flux. Since these light Zones are taken with their centersan equal dis-A tance apart, (these centers being the intersections of the 'axes with the line AB), the number of such light zones to be found in a unit length of c linder AB will be constant, and as the lig it flux directed to each zone is equal, the illumination of zone surfaces of equal area on the inside of cylinder AB will be the same. In other words, the illumination of the inside curved surface of the lower half of the horizontal cylinder generated b `revolving the line AB about the line LlV as an axis will be uniform. lf in designing the curve explained above the starting point-F is assumed the same as before, but if we beforehand set a definite limit for the curve, for instance, the line LT which makes an angle omega (o) with the initial line LM, then the limit of the altitudes of the flux measuring zones on the measuring circle EFE will be Q, the base of a perpendicular to line LM dropped from the .intersection of the line LT with the can define .one law 4of the final generating curve "FJ made with an infinite vnumberof f "parabolic sections, as follows:

Asa variable point l) moves along the curve from F to thefcurve limit J on the line LT, it must move`in Such a manner that the point R, which is the base of a perpendicular to line LM dropped from the intersection of the radius vector LP' with the measuring circle EFE, travels at a uniform rate from F to Q, in the same time that D, the inter- 4section with line AB of the variable axis corresponding to P, travels from one limit to the other of line AB at a uniform rate.

In the law just given, we have takenthe conception of one axis for the curve which swings around L between the limits LB and 'LA while its intersection with AB travels from B to A, insteadof a large number of axes'having their intersections spaced equal .distances along AB, as was our first conception.

Another law ofthe final generating curve FJ worked out above is that any increment of the curve at any point l? is a section of parabola with an axis intersecting AB at the variable point D which corresponds to the variable point It, the latter in turn being dependent on P. This law is evident from the way in which the curve is built up of infinitely small parabolic sectionsand it follows from this law that the length of the ran Y infinitely small sectionof parabola.

From what has preceded, curve FJ can be defined as a curve which starts at a given point F distance p from the focus L, the line LF making an angle beta with the initial LM and is limited by a given line LT ing vconditions hold.

which makes an angle omega with the initial line LlV. As the variable point on the curve P, moves from F to J the'follow- D moves from B to A 'or from A to B.

If while F moves from F toJ the point D moves from B to A in practice, the portions of the field of illumination farthest from the headlamp will be illuminatedby light reflected from the heel .of the reflector. On the other hand, if point D moves from A-to B under the saine circumstances, the farther portions ofthe eld of illumination will be illuminated by light from the front partv of the reflector. 1 R moves from F. to Q. Rimove's from F.'

to Q at a uniform rate as D moves from B` to A at a uniform rate. That is, the ratio of FQto FR is always the same as theV ratio BA to BD. y

In my description above I have described a reflector surface ofrevolution generated by a curve made up of a series of parabolic sections, the axis of each as well as the aXis of revolution beingV angularly displaced with respect to the others. I have also described the limit of this curve which is reached when the number of parabolic sections employed in its makeup is increased to,n infinity. It is understood that `I may employ, and that my invention includes, a reflector generated by I.

a curve made up of a denite or limited number of parabolic` sections arranged as described or generated by the limiting curve of a series of such parabolic sections when the number of such sections is increased to infinity. It is to'be pointed out that in practice'an approximate solution 'of the limiting curve only is required to secure uniy form illumination, on the desired field, be-

cause the source of light in practice is much larger than a point source and the spread of the beam resulting from this condition is sufiicientgto causethe reflector to give ap proximately uniform illumination when comparatively few sections of parabolae are employed in making up thegenerating curve of the refiector.

In the particular reflector 38 illustrated,

the generating curve shown as MN' onv Fig. 7 starts at the point N, which is in the vertical line passingthrough they point .O of reiiector 40, and extends counter-clockwise around its focus L to the point M, being limited by the radius vector making an angle of 130 with the horizontal axis of the headlamp. 4 With this arrangement the por-` tion of the finished reflector 38 near point M illuminates the more distant parts of the" field to be illuminated near B. (In this drawing the ground line of the field of illumination is indicated reduced, that is,pro

' jected toward the center of the headlamp.

llo

In reality this ground. line is very far from the headlamp compared with the size of the headlamp). This arrangement'of reflector 38 in the given case'is taken in order thatI the lower edge of the light beam from-reflector 38 inside the headlamp, M to B', will be as high as practicable in order to facilitate the placement of the auxiliary refiector 41. If the part of the reflector 38 Vnear M illuminated the field near A, the beam'of light within the headlamp would strike at a lower angle and less room would be available for the placement of reflector 41. The

point just brought out also leads to the principalv reason for placing `the electric lamp 29 in the peculiar position in which itsbase is elevated, making the center line meet the horizontal axis at anangle of .250." With this arrangement of electric-lamp 29 the point'M- of the reflector 38 will'behigher' above the horizontalaxis than if the'electric lamp29 were placedin a horizontal position land less room would be available for the placement of auxiliary reflector 41.

In reflector 38 illustrated the focusis L f on Fig.- 7. This focus corresponds tothe focus Lxof the generating curve ,FJ discussed above. 'The focus L for reflector 38 is. placed on the horizontal axis of `the-headlamp, at approximately the center of the filament of the electric lamp 29 used as the source of illumination.

The filament` ofany practical automobilev electric lamp which might be used as the source of illumination `in the headlamp, while small, is of fi-nite size 'and only roughly approximates a point source of light. For,v this vreason in operation the finished headlamp will give anactual beam having 4more spread than the theoretical .or computed beam for the given headlamp.`l This spread for any point on the reflector, for instance, M on refiector 38, see Fig. 7,Y will be equalV 'to the angle subtended at this point by the 'electric lamp filament..

Now in thefinished headlamp this spread of the 'actual beam for the most distant portion ofthe field to be illuminated must not be abovethe level of the headlamp, for if such is allowed, some light maystrike above the horizontal axis of the headlamp and cause glare. lInxthis headlamp the actual beamof lightvux from reflector 38 is confinedfbelow the level of the headlamp by the following method:

-The most distant-'edge of the theoretical field to be illuminated, which is assumed in designing the reflector, is taken sufficiently near to the headlamp so thatthe angle subtended at pointM with the horizontal is. as

great as, or greater than, the angle subtended at.poi ntM .by that portionl of thev electric lamp filament whichV is in' therear zontal and MB the line from 'M'to the distant edge of the assumed theoretical field to be illuminated, the-'angle HMB must'be as great as the angle subtended at by the rear half of the ainent. Having designed the reflector in t is manner, light coming from the rear edge 4of the filament to` reflector 38 will not be' reflected `at angles above the plane level of the headlamp.

Refiector 4() is designed in the same man- I ner as reflector38, except that its position is inverted with lrespect` to -reflector 38 and it feo is placed below the horizontal plane through the center of fthe headlamp.

The generating curve F0 on Figs. `7 and 8 for reflector 40 isUcomput'ed in the same manner as that for reflector v38. The reflecting'surface is generated vby revolving this of the, filament of the electriclamp 'in refiector 38,' the size of the filament of the 'electric lampssurce of light causes a spread- -ing of the reflected light beam in lreflector generating'curve FO through '18()O around the horizontal axis of the. headlamp, this revolving of the curve taking place in the dihedral angle subtended below vthe horizontal plane that includes the horizontal axis of thelamp. Y. I

The generating curve FO for reflector 4Q.

of the headlamp illustrated is assumed as starting at a point F on the horizontal axis 'of the headlamp, at a suitable distance in the rear ofthe center of the filament teclear the electric lamp 29, andis limited by the vradius vector which makes an angle of 300o .with the horizontal axis of the headlamp. (SeeFig. 7.)

rThe focus of reflector 40 is placed 'o n the horizontal axis of the headlamp at L, see' Fig. 7, which is at approximately the'center 29. As

40'.' This spread of the light beam is confined below. the level of the headlamp by the following method.

The most distant edge of the theoretical field to-be illuminated, which is assumed in V,designing the reflector, is takensufficiently near 'the headlamp so thatthe angle subtended at point Ol .(point O of refiector 40 and nearby portions illuminates the most distant portions of the field to be illumilnated) with the horizontal is as great as, or

lgreater than, the langle subtended at pointv .O by that portion-of the electriclamp filament which is infront of the focus L. rlhat is, if. OH isthe horizontal and OB the line from, O to the distantedge of the assumed theoretical field to be illuminated, the angle' 'HOB must be asgreat as the angle sub- '.40\.." The reflecting srface of reflector 41 is made by revolving a generating curve V XYZ on Fig. 7 about the horizontal axis o f the headlamp.. The generating Curve VXYZ is revolved ,approximately through 180o o f the upper dihedral angle subtended above the horizontal plane, which includes from llt)

the horizontal axis of the headlamp. The" intersections of this reflector by planes perpendicularto the horizontal axis at points within the` reflector are substantially semicircles, except that the semi-circles are not' carried all the way to the horizont-al` dia-A meters, a small space of about one-eighth of an inch being allowed to accommodate the central supporting plate 17- in the assembled headlamp.

The lower horizontal edge of reflector 41 is provided with a horizontal flange 113, and in the assembled headlamp the reflector is mounted on the upper` side of the .central supporting plate `17 and is held.'t othe central supporting plate 17 by screws, rivets vkor bolts which pass through the flange i3 and the central supporting plate 17; i

The reflecting surface of reilectorel is the inside surface which faces the electric lamp source of illumination. A portion of the inside surface of reflect-or 41 is radial in position from the electric lamp filament, and this portion is not included in the reflecting surface and is not polished.

The generating curve for reflector Ll1 1s made up of twoV ellipses VX and YZ, see Fig. 7, and a', straight line 4XY which 1s radial from the point L on the horizontal axis of the headlamp. The two ellipses have the same foci which are L and L ron the horizontal axis of the headlamp. The reflecting surface is generated by the two ellipses. lt is characteristic of a reflector from, a point source of light placed at one focus is focused or concentrated on the other focus. Therefore, if a point source of lightv is placed at focus L, all of its light flux reflected b f the reflector l1 will dpass through the point In desc'ri point- V is assumedalong the linefromL to N andbelow the line MB.l Since the curve is lall below the starting point, "the reflector 41 will not interfere with the light beam from reflector 38. Also, since V is taken along the line LN, no" light-from the filament of the electriclamp 29 can escape to`the outside of the headlamp between re flector 38 and reflector'41.

The first focusof the "ellipsea-'VX is assumed at L, which is at the center of the electric lamp filament. L is located as follows:

A line VlV is drawn from V, striking kthe reflector 410 at a aoint W at suchan angle W represented v, a [ray of' that if the line light traveling from V, 'this 'ray "would be reflected by reflector 40 to point B ofthe field to be illuminated; The point is loV ld` by trial.

lt is known from the laws1 reflector l() that "a ray. of light from L, the

which may readily be determined by calculation from`the mathematical principles used in computing the focus of the generating curve for Vreflector 10. After a trial posi bing the ellipse VX, 'the starting4 The second focus ellipse toward tion is selected for point` W, an angle BWD I andsince the angles LVV and BVVD areV i laid off equal, the' angle of incidence for Vl/V and of reflection for W'B must be equal with reference to reflector 40.;y Next a measwhether this line is parallel with either line MB or OB, and if found so, the line WB, if extended, will strike the point B of the field tobe illuminated, and W is the desired point on the generating curve of reflector 40. It is to be remembered that point B of the field to be illuminated is a'great `distance from the.. headlamp compared to the size of the headlamp.

Having foundA point W on reflector 40, the second focus for ellipse VX is taken at L', the intersection of line VlV and the horizontal axis of the headlamp.

The ellipse VX is drawn to X with foci L and L. The point X isplaced 'a' distance from the center line of the electric surface generated by an ellipse that the llght lamp 29 slightly greater than' half the diameter of the bulb. Both ellipses VX and YZ are limited at'their low points X and Z in this same manner in order that, with the finished reflector l1 assembled in the headlamp, the electric lamp 29 can be placed and withdrawn through the face of the headlamp without interference from reflector 41. i

urement of WB `is made to determine.`

The ellipse YZ is drawn from .an assumed l starting point Z on line XZ to the' radial line XY, meeting this limiting line in Y.

tlf it were not foriinterference with the placing of the electric lamp 29 by the completed reflector Ll1 in lthe assembled head; lamp, a reflector generated by' an ellipse made by continuing -VX to the horizontal axis or central supporting plate 17 would be satisfactory andthe offset ellipse YZ would be unnecessary. As a matter of fact,

the reflector 41 may be designed by a generating curve composed only ofthe ellipse VX extended downward as just described,

providedit is made detachable to accommoldate the placing'of the electric lamp 29,

fand it is understood that I may 'employ `such lkan .arrangement of reflector` 4.1 in the head lamp.

i Since theV reflecting surface of reflector focus of reflector 4.0, which strikes W will` be reflected to a certain portion o-f'the'field" of illumination, which We will call Duand,

4l is generated by thecurves VX and YZ, Aall hghtfrom L striking the said reflecting surface will be `reflected by reflector 41 to from l V, asv

pointed out above, strikes through L to l and as lwe travel along the .and f rom Y to Z, the relthe-portion FW of reflector 40. 'This light f being seen from Fig. 8 that light rays striking through L to point F are reflected to A,

- the' nearest point of the field to be illuininated. It can readily be. seen then that fol-k loWin the generating curve of reflector 41 from to X, Y and Z, thelight reflected from reflector 41 strikes reflector 40 and then is again reflected gradually over the'field to be illuminated from its distant edge B to its nearest edge A.

The :effect of reflector 41` with a point source of light at L can be conceived, also, vas though originating a point ysource of light -at L, which influencesor energizes from an illumination pointof view .the portion FW only of reflector 40. This point L is-an' apparent point of light or the image of point source L and vacts on reflector 40 lfrom F to W exactly as a point source of light placed at L.. Now L -in this character of a pointsource of light is taken just sufficiently ahead of L, the true focus of reflector 40, to vspread the beam-of F to W- all the Way from B to A offthe field of illumination. Since reflector 40 is designed to illuminate :the given field approximately uniformly, if the point light source is placed at L -it -Will also illuminate this field approximately luniformly from light fromthe .apparent point light source L Which energizes only4 the portion FV of reflector 40.

Reflector 41, therefore, receives light vfrom apoint source placed at its focus L and reflects it to reflector 40 in such a manner that it is again reflected so as to illuminate the field to be illuminated in an approximately uniform manner.

4v'In actual operation the filament of the electric lamp source ofillumination will be reflected by reflector 41l as an image in the vicinty of the secondary focus L. This image will `be the `same size as the real' filament and Will energize the portion FW only of reector 40. Now the image filamentat point L is asfar from portion FW of re.-

4flector 40 as the real filament, and being of the same size Willfcause nogniore spread of the light beam from reflector 40 than does the real filament. To insure against light Afrom reflector 41 striking reflector 40 and being directed at angles above the horizontal level of the headlamp, the most distant "edge ofthe assumed theoretical field to be illuminated by reflector. 41 is taken sufficiently near the headlamp so that the angle subtended at W (on reflector 40) with the horizontal (angle BWH) will be as great as the angle subtended at f by the forward h'alf of the image of the filament originated at L by reflector' 41. t

The curvature of the reffectors 38 and 4 in an intersecting plane including the' axis of revolution might be defined ina particular case as the limit of a series of connected parabolic sections having la common focus and-Whose axes are progressively angularly displaced from the axis of revolution, by which I mean that` the axesare successively angularly displaced from the vaxis of revo- I,lution 'in regular order, eachsucceeding axis being displaced from the axis of revolutionl through a greater angle than the preceding one.

I do not claimjas part of my invention in this case the particular structure of headv lamp illustrated in the drawings and which features a 'horizontal supporting plate or `partition to .Which the several reffectors are attached,ibut my invention refers moie particularly to the curvatures of the reflectors employed and to the peculiar combinations of such reflectors in relation to the light source and toeach other, and it is understood that any two or all three of these reflectors inay be employed, and if desired, the auxiliary reflector maybe omitted and the tip'of the electric lamp frosted, but I prefer, however, to use them in correlation as herein s described.

I claim:

l. A' reflector of revolution Whose curva.- ture" in'an intersecting plane including the axis of revolution is a curve made up of, a connected series of parabolic sectionsivhose Aaxes are angularly displaced with respect to each other.

2. A reflector of revolution Whose curva- 'ture in an intersecting plane including the face is composed of 4connected zones, the

curvatures of the zones in an intersecting plane including the axis of revolution being parobolic sections having a substantially common focus but the axes of which parabolic sections are progressively angularly displaced from the axis of revolution, andv the areas of which zones are suchtliat each zone intercepts a substantially equal amount of light flux from a light source'placed at the-common focus.

4. A reflector of revolution whose surface is composed of a series of zones, the zone surfaces having a substantially common focus, the curvatures of the zones in an intersecting plane including the axis of revolution being parabolic sections Whose foci coincide with the said common focus of the 45 1 posed of ellipsoidal portions placed in front rones and whose axes', are progressively angularly displaced from the axis of revolution in such a manner that they intersect the central points of successive and equal lengths on the line in the field to be illuminated, which is parallel to the axis of revolution in the said -intersecting plane', and the areas of Which zones are such that each zone intercepts a substantially equal amount of light flux yfrom alight source placed at the common focus of the zones.

5. In a headlamp, a reflector Whose reflecting surface is generated by a lane curve rotated about an axis, and W iich plane curve is a series ofl conic section portions Whose axes are progressively angularly displaced from the axis of revolution.

6. lna headlamp a combination of two 'reflectors of revolution, one being a reflector Whose curvature in an intersecting plane in cluding the axis of revolution is a curve made up of a series of parabolic sections Whose axes areprogressively angularly displacedfrom the axis of revolution, andthe other reflector being an ellipsoidal portion placed on the opposite side of the light source and so positioned as to reflect light from the light source onto the first reflector:

7. In a headlamp, a combination of three reflectors and a light source,"onel reflector being located above and in the rear of the light source and having a surface of'revolution' Whose curvature in an intersecting plane including the axis of revolution is a curve composed of a series of parabolic sections whose axes are progressively angularly -displaced from the'4 axis of revolution, a sec- 0nd reflector located in the rear. of and below the light source and having a surface of revolution Whose curvaturev in an inter# lsecting plane including the axis offrevolution is a `curve composed of a series of parabolic sections whose axes are progressively angularly'displaced from the axis of revolution, and a third reflector of-revolution comof the light source and positioned so as to reflect light from the light source onto the reflector located below and in the rear of the light source. i.

8. A reflector of revolution Whose curvature in an intersecting plane including the axis of revolution isa curve made up of a connected series of parabolic sections having a common focus `and Whose axes are progressively angularly displaced from the axis of revolution in'such a manner that they intersect equally spaced points on the line in the eld to be illuminated which is paral-` lel to the axis of revolution in the said intersecting plane, and rWhich parabolic sections are of such lengths that the -arcs on any small measuring circle having the common focus as a center, subtendcd by the radius vectors from the common focus to` the extremeities of the parabolicsections, have projections of equal length `on the axis of tions having a common focus and Whose axes are progressively angularly displaced from the axis ofv revolution in such a mannerthat they intersect equally spaced points on the line inthe field to be illuminated which is parallel to the axis of revolution in thesaid mon focus as a center, subtended by the radius vectors from the common focusto the extremities of the parabolic sections, have projections of' equal length on the axis of revolution. i

10. In a headlamp, a combination of tivo reflectors of revolutiom'one being a reflector Whose surface is composed of. a series of zones Whose cuivatures in an intersecting plane including the axis ofv revolution are parabolic sections having aV common focus 'intersecting plane, and which parabolic seci tions are of such lengths that the aics on any small measuring circle having the comj and whose axes are progressively angularly Y displaced from the axis of revolution in such a manner that they intersect equally spaced points on the line in the eld to be illuminated that is parallel to the axis ofrevoliition inthe said intersecting plane, and 4thc areas of which zones are such that each zone inter-v cepts a substantially equal amount of' light flux from the light source placedl atl the on the opposite side of the light source and having one focus at the center of the light source, and so positioned as to reflect' light from the light source to the first reflector.

l1. In' a headlamp, a combination of two reflectors of revolution in which one reflector is an ellipsoidal reflector placed in reversed position ahead of the light source4 and arranged to project an image of the light source at a point adjacent to the light source, and in which combination the other reflector is placed in the rear of the light source and has. a surface composed of a series of connected zones. having. a common focus and-having `curvatures in the intersecting plane includ'- ing the axis of revolution Which are paraboiic sections Whose foci coincide With the common focus of the zones, and whose axes -intersecting plane, and thel areas of which Zones are such that each z'one intercepts a substantially equal amount of light flux from the light source which is placed at the common focus of the zones, and which reflector is arranged to receive light fromLthe light source and also to receive light from the said image of the light source.

12. In a headlamp, a light source, a-front` reflector of. revolution reversed in position and placed in front of and above the level -of the light source, and which front reflector has a reflecting surface of ellipsoidal portions having common foci, and which surthe center of thelight source, and which zones have curvatures in the intersecting plane including the axis of revolution which are parabolic sections having a common focus at the said common focus of the zones, and the axes of which `parabolic sections are progressively angularly 'displaced from the axis of revolution in such a manner that they intersect equally spaced .points on the line in the field'to be illuminated which is parallel the light source, and' which front refiector and rear reflector are arranged on a common axis of revolution which passes through Ithe center of the light source, and which rear reflector receives light from the light source and from the said image of the light source and reflects the light so received through the face of the headlamp in a beam that illuminates uniformly a semi-cylindrical surface outside the headlamp which is parallel to and concentric with the axis of revolution of the reflectors. s

In testimony thatl claim the foregoing, I have hereto set my hand, this 22nd day of March, 1920.

- CHESTER N. WEEMS. 

